With the popularity of white noise machines and apps that play soothing sounds, such as raindrops on a roof and ocean waves, or actual white noise, you might think there’s firm proof that these ...

Getting a good night’s sleep is hard. A third of all American adults report getting less than the daily recommended amount of sleep nearly every night. Too little noise, and the mind starts to race.

“The sound machine can generate any of several types of sound, from nature [or] music,” Dr. Cory Portnuff, an audiologist at the University of Colorado Health’s Hearing and Balance Clinic, says. In ...